The production of flat sheet glass by the float glass process involves the melting of glass in a melt furnace and the transfer of the molten glass from the melt furnace to a float glass forming chamber. There the molten glass is poured onto a bath of molten tin within the float glass forming chamber. To prevent the surface of the hot tin from oxidizing, an atmosphere of nitrogen is used in the float glass forming chamber. The atmosphere also contains hydrogen which reacts with any oxygen which is present to form water vapor, and with sulfur generated from the glass to form hydrogen sulfide. This further ensures the integrity of the hot tin and the molten glass within the float glass forming chamber.
In the making of glass a very large amount of heat is needed to melt the glassmaking materials as they are processed in a glassmelting furnace. Generally this heat is provided by the combustion of fuel and oxidant which has heretofore generally been air.
Nitrogen oxides (NOx) are recognized pollutants and it is desirable to reduce emissions of NOx from industrial processes. NOx is produced in air-based combustion mainly because at the high temperatures of the combustion reaction, nitrogen from the air combines with oxygen.
Recently in response to the NOx problem many industrial processes have begun using pure oxygen or oxygen-enriched air to carry out the combustion as this reduces or completely eliminates the nitrogen brought into the area of the combustion reaction by the oxidant. However, the use of pure oxygen or oxygen-enriched air as the oxidant increases the costs of glassmelting and thus of the entire glass manufacturing system.
Accordingly it is an object of this invention to provide a float glass manufacturing system which employs oxygen as the oxidant for combustion to generate heat for the glassmelting furnace and which operates more efficiently than conventional float glass manufacturing systems.